X-ray tube



y 1952 M. POITTEVIN 2,597,817

X-RAY'TUBE Filed NOV. 50, 1946 3 sh t h 1 M. POlTTEVlN May 20, 1952 X-RAY TUBE 3 Sheets$'neet 2 Filed NOV. 30, 1946 May 20, 1952 Filed Nov. 50, 1946 M. POITTEVIN X-RAY TUBE 3 Sheets$heet 5 Patented May 20, 1952 UN [TED ST PATENT OFFICE Application November 30, 1946, Seria l'No. 713,354 I In. France December 14, 1945 8 Claims. (Cl. 313-57 The present invention has for its-objectan improvement in electronic X-ray tubesand permits of obtaining focus of extreme sharpness.

It consists-in giving to the axis of thefilament which emits the electrons a radius of curvature of which the centre is located on or near the front surface'of the anticathode, this filament being situated ina focussing member which may also be of curved form.

Under these conditions, in the plane contain-' ing the curved axis of the filament, the lines of electric force emitted by this filament converge first towards the centre of curvature of the lat ter, then, become perpendicular to the surface of the anticathode. The electrons emitted by the filament, the paths of which are approximately the straight prolongations of the initial part of the lines of force, then converge towards the centre of curvature of the filament, so'that,

if thecentre is disposed on the face of the anti-' The major axis of the focus may therefore be placed in a plane perpendicular to that'which contains the curved axis of the filament, whilst, in ordinary X-ray tubes, the major axis of the focus and of the filament are on the same'plane.

So that the dimension of the focus may be very small in the 'plane of curvature of the filament it may be necessary either to cool the extremities of this filament to limit its emissionto'its correctly curved central part, or suitably to adjust the electric 'field in the neighbourhood of these extremities by means of suitable electrostatic-members.

Itis suitableals'o to give to the face ofthe anticathode on which thefocus is disposed any appropriate form and to incline its adjacent faces so as to regulate the convergence of the lines of force. v

The electron emitting filament may be constituted byan elementthe emissive part of which is curved and may consist of a helix witha curved axis and of suitable section or more simply of a wire or by a ribbon.

One "can, therefore, regulate the dimensions of the focus, after construction of tube, by variation of the curvature of the filament or of the distance between the filament and the anticathode.

Figs. 1, 2 and 3 represent a tube made in accordance with the present invention.

In thesefigures: l is the anticathode, 2 is a helicoidalfilament, 3 is the curved axis of radius 1' of filament '2, the axis of the curvature of said filament being perpendicular to a plane containing the length of the filament is illustrated at the point 4 on the'front surface of [.but point 4 maybe located outside this surface for instance between the filament and the anticathode.

5 is a channeled focussing member shown in section, the'curved surfaces of which as shown in Fig. 1 are concentric about the centre 4, but it may have a different curvature or even-be flat as if the lines 5' and 5" were straight.

6 is a rod supporting the member 5. I and l are rods used simultaneously as mechanical supports for filament 2 and as conductors for its heating current. 8 is the housing of the X-ray tube comprising sealed entry points of therods 6,1 and 1'.

9 represents lines of force, It! represents paths of electrons which coincide with the lines of force'in the neighbourhood of the filament.

The fo'cusis disposed on the surface of anticathode I and may coincide with point 4 or not according to where this'point is located as already explained.

The members 'l-and 7' may have'any proportions andbe extended towards the filament'to limit the "emission of the latter to its central part.-

The'extremities of the members I and 8 at the right of Figs. 1 and 2 are not shown and may be of any suitable known shape and disposition.

Figs. 4, 5,6 an'd '7 show difierent forms of the member-5 permitting tosecure'suitable lines of electric force in the neighbourhood of the-extremities of the filament.

In Fig.4 the member 5 comprises the extremities --5 between which thefilament is encased.

In Fig. 5 the member 5 carries the members H of the same diameter as thatof'the filament and located as prolongations of the latter.

In Figs. 6 and 7 the members-5 carry-mem- 3 bers I8 and is of different form from parts but for an analogous purpose.

Figs. 1 and 3 show, besides the general disposition which is the subject of the present invention, a means of adjusting the dimensions of the focus in the plane of the filament by the adjustment of the curvature of the latter, by a means of the supports 1 and I which can oscillate for this purpose.

II and H are fluid-tight and deformable members soldered, brazed or otherwise sealed on the one hand on the envelope 8, and on the other hand, to the rods I and 1. The members II and H allow, by their deformability, some turning of rods I and l" about points I2 and I2. The result is that the extremities I3 and I3 separate when the extremities I4 and I4 converge and conversely; this allows adjustment on the radius r by controlling the distance between l4 and l4.

I5 is an insulating member carrying screws l6, allowing the alteration of distance between H and Hi. The member l5 may furthermore be fixed onto the rod 6 or on to any other member rigidly fixed on the envelope 8.

This adjustment device of the radius of curvature of the filament is only given by way of example and any other equivalent method may be used, for instance the deformation of bimetallic supports heated directly or indirectly by the heating current of the filament or by a different current which depends or not on the latter.

Figs. 8, 9 and 10 show an X-ray tube allowing the adjustment of the dimensions of the focus to be made by the control of the distance between the cathode and the anticathode.

In these figures, 2| is the insulating envelope of the tube, 22 is the electron emitting filament. This filament 22 is formed by a simple metallic wire, the axis 23 of which has a radius of curvature r the axis of the curvature of said filament at 24 being perpendicular to a plane containing the length of the filament.

The channeled focussing member 25 is so formed that the centre of curvature of the lines 25 and 25" is the same as the centre of curvature of the filament. However, these two centres may not coincide and may even be separated by a distance extending to infinity, that is to say that the filament 22 may be rectilinear and the lines 25 and 25" curved or the filament 22 may be curved and the lines 25 and 25 rectilinear. 26 is a rod sealed in envelope 2| and carrying the member 25; 21 and 21' are two rods sealed in the envelope 2| and used simultaneously as mechanical supports for the filament 22, and as electric conductors for its heating current.

To filament 22 and to rods 21 and 21' such lengths and diameters are given that the ends of the filament whence emerge the aberrant lines of force may be sufficiently cooled by rods 21 and 21' in order not to emit electrons. 28 is a truncoconical tube sealed at one end to the envelope 2| and soldered, brazed or otherwise sealed by the other to the part 29 of the anticathode. The part 29 has a screwed end which carries the movable part 39 of the anticathode which is screwed freely on it.

35 are paths of electrons which, at their origin coincide with radii T but which slightly separate therefrom, later on, so that the focus 34 does not coincide with centre 24.

36 is a ring fixed on 39 which may be magnetic or made of material similar to the rotor of an induction motor.

31 is a magnetic circuit placed in the same plane as 36 and comprising poles 33, 39, 4|], 4|; poles 38 and 49 being excited by the circuit 42 and the poles 39 and 4| being excited by circuit 43.

Circuits 42 and 43 are fed by a common source of direct current 44 and closed successively by switches 45 and 46, in a sequence which depends on the position of the double-switch 41.

The arrangements described above permit experiments to be made to find the best dimensions of the focus by the adjustment of the distance between the cathode 22-25 and face 33 of the anti-cathode. Th'm adjustment is made by rotation of part 30 for instance by communicating to the X-ray tube angular asymmetric accelerations by any known manual or mechanical means. In this case elements 36 to 41 shown in Figures 8, 9 and 10 are useless.

The rotation of part 39 may also be made by means of part 36 and by an oscillating magnetic field produced by elements 31 to 47.

Fig. 8 is, with regard to this, sufficiently clear for it to be understood that if the switches are worked in the following sequence: closure of 45. c1osure of 46, opening of 45, opening of 46-, there is applied to the part 36 a magnetic field the orientation of which alters sharply when switch 46 is closed, which induces currents in 36 and the reaction of this current on these induction fields makes assembly 3933 revolve through successive angles.

The direction of the rotation of the field and in consequence the direction of the rotation of the anticathode may be reversed by means of the double-switch 41.

In any case, the position of parts 39 to 36 relative to 29 may be shown by means of any suitable marks on parts 29, 39 and 36.

After adjustment of the dimensions of the focus part 29 of the anticathode may be expanded with the double purpose of immobilising the movable part and of obtaining a thermic contact between 29 and 39 favouring the removal of the energy received by the focus. This expansion may be obtained by dudgeonage, or by any other equivalent method.

Figs. 11 and 12 show X-ray tubes made in accordance with this invention and using different means for adjusting the distance between the cathode and the anticathode.

In these figures the same reference numbers represent the same parts or members as in the preceding figures. 59 is an anticathode of an already known type. 5| is a deformable corruated tube made of metal or suitable alloy so that its dimension parallel to the main axis of the tube may be altered without prejudice to its fluidtightness.

This tube 5| may be fixed to the envelope 2| directly or by means of intermediate tubes 52 and 53 which are sealable or may be soldered to 5| and 2|.

Figs. 11 and 12 are only given by way of example and tubes 5|, 52 and 53 may be located in any convenient position.

The adjustment of the distance between the members 25 and 50 and the immobilisation of the movable members after adjustment may be made by any known means the description of which would be outside the present patent specification.

Figs. 8, 9 and 10 show, besides the device for adjustment of the distance between the filament and the anticathode, one shape of the latter a1- lowing the adjustment of the electric field in which the electrons are moving.

Part 30 comprises two oblique faces 3| and 32 which form limits to the face 33 on which focus 34 is formed.

The face 33 has therefore a rectangular form, the length of which is equal to the diameter of part 3!! and with a much smaller width than this diameter; but the oblique faces 3| and 32 Y may be replaced by a trunco-conical or pyramidal surface terminated by a circular or polygonal face 33 on which is disposed the focus 34.

What I claim and wish to secure by Letters Patent is:

1. In an X-ray tube, means for improving concentration of the electrons adjacent the focus comprising a focusing member with a channel containing a filament member, at least one part of which has a concave curvature centered adjacent the focus, the axis of the curvature being perpendicular to a plane containing the length of the filament.

2. In an X-ray tube, means for improving concentration of the electrons adjacent the focus comprising a filament member with a'rectilinear axis and a focusing member having a channel containing said filament member and a concave curvature centered adjacent the focus, the axis of the curvature of said channel being perpendicular to a plane containing the length of the filament.

3. In an X-ray tube, means for improving concentration of the electrons adjacent the focus comprising a filament member having a concave curvature the axis of which is centered adjacent the focus and a focusing member having a channel containing the filament member and a concave curvature centered adjacent the focus, the axis of the curvature of said channel being perpendicular to a plane containing the length of the filament.

4. In an X-ray tube, means for improving concentration of the electrons adjacent the focus comprising a focusing member with a channel containing a filament member, at least one part of which has a concave curvature centered adjacent the focus, the axis of the curvature being perpendicular to a plane containing the length of the filament, and electrostatic members in the neighborhood of the prolongation of the extremities of the filament member for centering the electric field.

5. In an X-ray tube, means for improving concentration of the electrons adjacent the focus comprising a focusing member with a channel containing a filament member, at least one part of which has a curvature centered adjacent the focus, the axis of curvature being perpendicular to a plane containing the length of the filament, an anticathode on which the focus lies, and inclined faces on said anticathode, whereby the electric field in which the electrons are moving is suitably regulated.

6. In an X-ray tube, means for improving concentration of the electrons on the focus comprising a focusing member with a channel containing a helical filament member, at least one part of which has a concave curvature centered adjacent the focus, the axis of curvature being perpendicular to a plane containing the length of the filament.

7. In an X-ray tube, means for improving concentration of the electrons adjacent the focus comprising a focusing member with a channel containing a wire filament member, at least one part of which has a concave curvature centered adjacent the focus, the axis of the curvature being perpendicular to a plane containing the length of the filament.

8. In an X-ray tube, means for improving concentration of the electrons adjacent the focus comprising a focusing member with a channel containing a ribbon filament member, at least one part of which has a concave curvature centered adjacent the focus, the axis of curvature being perpendicular to a plane containing the length of filament.

MAURICE POITTEVIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 793,112 Wagner June 27, 1905 1,174,044 Benson Mar. 7, 1916 1,310,714 Rider July 22, 1919 1,559,714 Lilienfeld Nov. 3, 1925 2,111,940 Schlesinger Mar. 22, 1938 2,130,020 McEuen Sept. 13, 1938 2,157,718 Mutscheller May 9, 1939 2,240,120 Nicoll Apr. 29, 1941 2,268,196 Pierce Dec. 30, 1941 2,329,320 Atlee Sept. 14, 1943 2,350,269 Atlee Ma 30, 1944 FOREIGN PATENTS Number Country Date 586,817 Germany Oct. 26, 1933 818,476 France Sept. 27, 1937 

